1. Field of the Invention
The present invention generally relates to graphical pointing devices for indicating locations on a display such as cursor controllers and, more particularly, to devices capable of pointing to and/or selecting locations on a display and/or manipulating displayed images such as icons or other indicia which may be displayed at such locations.
2. Description of the Prior Art
In the field of computers and data processors, it has long been recognized that the capability of a user to receive and assimilate information in order to interact easily with the computer is of major importance in the usefulness of the computer in many applications. The utility of increased "computing power" to execute programs at ever increasing speeds diminishes in all but a relatively few highly complex programs which require only slight interactivity with a user when the user cannot readily perceive, understand and react to the results thereof. Therefore, the interest in and dedication of a significant fraction of available computing power to the user interface has become a widely accepted practice for both hardware and software design in the data processing field. In recent years, it has also been found that displayed graphics images, especially if manipulable by the user, provide a particularly good medium for both the communication of information to the user including processor and program execution status and for the input of user control information and data.
Input of control signals and data through the medium of a graphic display requires the use of a device by which a location on the display may be specified and a separate mechanism for selection. This latter requirement is imposed by the requirement of positional feedback to the user by display of a cursor, icon or the like so that the operator can control the specification of a location without inputting of data or exercising control until the location is correctly specified. In the past, this has been accomplished with various devices which have become well-known and which are in widespread use, such as the mouse, light-pens, trackballs (essentially an inverted mouse which does not meed to be moved across a surface), gimballed and isometric joysticks and many special purpose arrangements such as adaptations to accommodate various physical disabilities of the user which will hereinafter be referred to collectively as graphic input devices.
Typically, these devices will include one or more buttons (e.g. the well-known one-, two-, or three button mouse) or switches by which a control function can be effected once a location on the display has been correctly specified to the user's satisfaction. Occasionally, a mechanism such as a treadle switch is employed which is entirely separate from the apparatus used to specify a location on the display. In any event, both types of control (e.g. location and selection) must be provided.
In recent years, there has been not only a trend toward miniaturization and portability of data processing devices but also toward ergonomic design and "human engineering" so that the devices may be operated in a manner which may be more familiar to a user. A major difficulty with miniaturization is the size of input devices, such as a keyboard which rapidly become less acceptable as size is diminished. This need for smaller input arrangements has led to the development of so-called pen computers in which data may be entered by an act similar to writing on paper in a notebook. For the same reason, trackball devices which may be included in the housing of the portable computer and do not require a separate surface for operation by a user are often included. More recently, isometric joysticks which do not significantly move but control cursor motion in response to force applied thereto have appeared in commercially available devices.
Regardless of the degree of miniaturization which may be possible, the requirement of separate means to provide the separate functions alluded to above requires separate space which must be compatible with the physical size of a user. Therefore miniaturization is limited by this practical limitation which is independent of any design feature of the data processing device itself. The only alternative to the provision of separate controls is to combine the functions of devices which sense the user's actions. When this is done, separation of functions is difficult.
For example, if a pressure or force sensor is included in a stylus-like position control device, such as a light pen or joy-stick, alteration of force during normal motion over the display often causes unintended selection even though a separate sensor on an axis orthogonal to other sensors is provided. Conversely, the user's action in changing force applied against the display usually causes small but often significant change in the location specified. These problems are generally associated with the fact that a stylus will not often be naturally or comfortably held in a position in which its axis is perpendicular to the display. For example, a correction technique for use with a light pen or touch screen where positional errors were caused by lifting of the pen (for selection only) in a direction not precisely orthogonal to the display screen is disclosed in U.S. Pat. No. 4,558,313 to Garwin et al., which is hereby fully incorporated by reference. This latter difficulty is also characteristic of the well-known gimballed joy-stick (which is not likely to be in a neutral or "vertical" position when a location is being specified) or a mouse in which the natural stroke of a finger on a button is not perpendicular to the surface on which it is moved (or, alternatively, the stroke of the button motion is inclined in the interest of a more natural feel to the user).
These problems in the practical use of graphical input devices have proven quite intractable, particularly as increased degrees of miniaturization have been attempted. Further, attempts to facilitate or enhance separation of functions by sensing of force, with or without electronic processing of the transducer output, has met with little success due, at least in part, to the differences in force applied by different users in the comfortable actuation of the device and/or variation in the nature of actions by even a single user. For example, the amount of force applied to a stylus by a user may vary greatly with stress: when successful tracking of position is not being achieved, it is a natural reaction to increase force of the stylus against the display, even though the degree of force already applied may be the reason for incorrect tracking.
All electronic processing of signals from transducers in graphic input devices attempted in the past for detection of selection has also been complicated by the need to accommodate sensing of a change in location specified by the user during periods of selection for common display manipulations such as "dragging" of an object. During such operations, the signals from the transducers must necessarily change because of the operator manipulation for positional input. These signal variations may complicate the detection of selection and deselection. Further, force applied to a stylus or selection button by an operator may vary widely (due, for example, to irregularities in the surface over which the pointing device is moved or as an incident of the changing positional input by the user) and rapidly while applied force remains relatively high.
Accordingly, such operations have been difficult without the provision of separate selection and position input arrangements.